Electric welding generator



March 5, 1935.

L. M. RICHARDS ELECTRIC WELDING GENERATOR Filed July 24, 1930 Patented Mar. 5, 1935 i UNITED STATES PATENT OFFICE ELECTRIC WELDING GENERATOR Lee M. Richards, Dayton, Ohio, assignor to The Master Electric Company, Dayton, Ohio, a corporation of Ohio Application July 24, 1930, Serial No. 470,349

Claims. (Cl. 171-225) This invention relates to electric generators for main field circuit or in the exciter shunt circuit. use in electric welding systems or the like wherein For some conditions of use, both a series and the generator is subjected to a variable load reshunt winding in the exciter field or in the main sistance and particularly to a generator of the field are found desirable.

5 shunt-field type which will afford a relatively high \The object of the invention is to simplify the 5 are striking voltage, and a current varying inconstruction as well as the means and mode of versely as the voltage, which in turn fluctuates operation of electric welding generators and the as the resistance of the are changes during the like, whereby they will not only be cheapened welding operation thereby maintaining substanin construction but will be more efiicient in operl0 tially constant wattage with minimum loss of ation, uniform in action, and capable of producpower and affording in the arc the uniform heat ing strong welds with ease of operation by modnecessary to insure a strong homogeneous weld. erately skilled workmen.

Arc welding operations necessitate a generator A further object of the invention is to obviate having a drooping voltagev characteristic. the necessity for relatively large and heavy rel5 When not subjected to load, the voltage at the actance in the welding circuit with its increased terminals builds up to a relatively high potenweight and cost. tial, affording the necessary voltage to strike the A further object of the invention is to provide arc. As load is applied by approach of the eleca generator affording high initial striking voltage trode to the work, the voltage drops in value to and constant wattage at variable potential prothat required to maintain the arc, varying with portionate to the resistance of the maintained 20 the variable resistance of such arc. are.

There are various ways of obtaining this A further object of the invention is to provide "drooping voltage characteristic. A resistance a generator which will very quickly adjust itself of suitable value may be placed in series with the to sudden changes in the loading circuit by autowelding arc to which current is supplied from matically increasing and decreasing the voltage 25 a constant potential source. Such arrangement as the resistance of the load increases or deis uneconomical sincetoo great a proportion of creases, thus maintaining within reasonable the current supply is dissipated through the relimits af relatively constant heat in the arc. sistance and is unavailable for useful work. An- A further object of the invention is to provide other method of achieving the drooping voltage means for insuring maintenance of proper polarity 30 characteristic is by use of a field winding in series of the exciter armature. with the load, so connected as to oppose the main A further and important object of the invenshunt field. Such construction is expensive and tion is to minimize the power losses of welding presents manufacturing difliculties, and moreover generators.

P is inefficient due to losses in the series field. A A further'object of the invention is to provide further method of obtaining the desired droopa construction which will involve minimum maning voltage characteristic is by means of two ufacturing difficulties and production problems, shunt windings, one of which is self-excited, and and which will be economical in operation. the other separately excited. This also involves With the above primary and other incidental expensive production operations. A self-excited objects in view, as will more fully appear in the 40 winding alone is unreliable, as such self-excited specification, the invention consists of the feagenerator sometimes fails to build up the necestures ofconstruction, the parts and combinations sary voltage and does not produce a suitable thereof and the mode of operation or their equivdrooping voltage characteristic. The objecalents as hereinafter described and set forth in tions to these various methods of operation are the claims.

' overcome by the hereinafter described construc- Referring to the drawing, Fig. 1 is a diagramtion. matic view of the generator and welding circuits In the present generator construction there are embodying the fundamental features of the presemployed a generator armature and an exciter arent invention. Fig. 2 is a similar diagrammatic 5 mature connected in series with each other and view illustrating a series winding in the exciter with a single shunt field winding-of the main field. Fig. 3 illustrates a further modification generator. Thus the field of the main generator wherein the exciter field contains a series winding I is both self and separately excited by the comonly. bined voltage of the two armatures. The current Like parts are indicated by similar characters I setting is controlled by a rheostat either in the of reference throughout the several views.

In the drawing there is shown a shunt generator, the shunt field of which is both self and separately excited. The generator armature 1 and the exciter armature 2 are connected in series with each other and with a generator field winding 3 included in the shunt circuit connecting the two armatures 1 and 2. This shunt field winding is therefore simultaneously subjected to the combined voltages of both the generator armature 1 and exciter armature 2. The exciter is additionally provided with its individual shunt of electrode by means of a rheostat 8 located in the common shunt, or in lieu thereof, by a rheostat 9 located in the exciter shunt. Either of the rheostats 8 and 9 may be used to set thecur- I rent independently of the other rheostat. Since the current fiow in the rheostat is small in value" and the resistance relatively small, but very small loss is caused by the rheostat. Inasmuch as the main generator armature acts as a regulator, the rheostat is not required for control purposes but only for initially determining the current flow for different welding operations, and is not cssential to the proper functioning of the apparatus if the windings are designed and proportioned for the particular load. A reactance 10 may be included in the welding circuit to prevent current surge or sudden changes of current which might otherwise take place at the time of striking the are or due to are variation.

The fleld3 being under the influence of both armatures 1 and 2 is subjected to a substantially constant degree of excitation by the exciter armature 2 and to a variable degree of excitation by the main generator armature 1, depending upon and varying with the value of the resistance load in thewelding circuit When the welding circuit is open, due to disengagement of the electrode from the work, the terminal voltage builds up to relatively high potential. As soon as the circuit is closed by contact of the electrode with the work, there is a temporary short circuit causing a large amount of current to flow and producing a drop in the voltage from the armature 1. Since the field excitation is the sum of the voltages from the armatures 1 and 2, there is a reduction of the field excitation which causes further drop in the terminal voltage. This holds the current in the arc circuit down to reasonable value on short circuit and on low resistance loads. As the electrode is moved slightly away from the work, an arc is formed which increases the resistance of the load circuit. By such increase of resistance, the current fiow through the armature coils is decreased and the voltage is increased at the armature terminals sufliciently to maintain the arc across the higher resistance gap. Accordingly as the arc resistance increases, the strength of the field 3 will increase and tend to maintain the heat of the arc constant. As the fiow of current through the arc increases, the strength of the field 3 will decrease, thus reducing the voltage at the arc in accordance with the well-known action of a shunt field, and maintaining within reasonable limits the heat of the arc. This construction has the advantage of quick adjustment to sudden load changes. The influence of the exciter armature upon the controlling field 3 being unafiected by the variation of load resistance, maintains a workable power balance under extreme conditions.

The construction as heretofore described is subject to various modifications and additions without, however, changing its fundamental characteristics.

A further modification is illustrated in Fig. 2 wherein a supplemental winding 12 is interposed between and in series with the armatures l and 2. This series field winding may be subjected to the influence of either the main armature l or exciter armature 2. It is shown for illustrative purposes as a part of a compound winding for the exciter, while in Fig. 3 it is shown as the only field winding for the exciter armature 2. Such supplemental series field assists in providing additional drop in the generator voltage, and incidentally will tend to maintain proper polarity of the exciter armature.

As before mentioned, direct current from other source may be employed for exciter purpose. In such case the armature 2 and its field winding 4 are omitted and opposite sides of a direct current power line are connected at 13 and 14, as indicated in Fig. 1, which has the effect of disposing the power station armature 15 in the field circuit in series with the main armature 1 and field winding 3 in lieu of the exciter armature 2.

While the use of reactance 10 may be desirable for certain conditions of use, it will ordinarily be unnecessary. By the automatic inverse fiuctuations of current and voltage as the arc resistance changes, the machine automatically compensates for resistance variation to such extent that current surge is minimized.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific details shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect and the invention is, therefore, claimed in anyof its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. In a dynamo electric machine of the character described, a pair of generators having the armatures connected in series, a short shunt field winding and a series field winding cumulatively connected supplying excitation to one armature, each of said windings being subject to the influence of both armatures, a second shunt field winding influencing the other armature only so as to produce a drooping voltage characteristic output from said other armature, and a working circuit including a variable resistance load supplied with current from said other armature alone.

2. In a dynamo electric machine of the character described, a pair of generator armatures, a shunt field winding and a series field winding,

each subject to the influence oi both armatures, and a second field winding pertaining to its armature only and cumulatively connected with respect to said series winding so as to produce a drooping voltage characteristic output from one of said armatures, and a working circuit supplied with current from said armature having a drooping voltage characteristic.

3. In a dynamo electric machine or the character described, a generator, acumulatively compound wound exciter for said generator, the armature ot the generator and the armature of the exciter being connected in series with the series field of said exciter, the shunt winding of the generator being connected in parallel with the armature and in series with the exciter armature, the phase relation of said fields being arranged to maintain proper polarity of the output and arranged to produce a drooping voltage characteristic output from said generator.

4. In a dynamo electric machine having a gen erator and a shunt wound exciter, the method output from said generator.

including the influencing oi the armature or said generator by a fiux component responsive to the voltage output or said generator andby a flux component responsive to the current output of said exciter, the output of said exciter being influenced by a field responsive exclusively to the potential of. said esciter, and a field responsive to the current output of said exciter and the voltage output of said generator so as to produce a voltage output from said generator having a drooping voltage characteristic.

5. In a dynamo for an electric machine of the character described, a shunt-wound generator, a cumulatively compound wound exciter for said generator actuated in series with the shunt winding thereof, the armature oi the generator and the armature of the exciter being connected in series with the series field of saidexciter and connected in series with the shunt field of said generator so as to produce a drooping voltage 20 LEE M. RICHARDS. 

